/***********************************************************************
Write a recursive function called `sum` that takes an array of integers
and returns the value of all the integers added together. Your array may
include a mix of positive and negative integers!

Examples:

sum([1, 2, 3]); // => 6
sum([0, 1, -3]); // => -2
sum([1, 2, 3, 4, 5]); //=> 15
***********************************************************************/
//sum([1, 2, 3, 4, -5]); //=> 10
//base case: arr.length === 0
//recursive case: arr.length > 0
//recursive step: arr.slice(1)



function sum( arr ) {
  if ( arr.length === 0 ) {
    return 0;
  }
  return arr[ 0 ] + sum( arr.slice( 1 ) );
}

/**************DO NOT MODIFY ANYTHING UNDER THIS LINE*****************/
module.exports = sum;
